9-substituted-8-oxo-adenine compounds as toll-like receptor (TLR7) modulators

ABSTRACT

The present invention provides compounds of formula 
                         
where n, R 1 , R 2 , A, X 1 , Y 1 , Z 1 , X 2  and Y 2  are as defined in the specification, processes for their preparation, pharmaceutical compositions containing them and their use in therapy.

RELATED APPLICATIONS

The present application is a U.S. National Phase Application of International Application No. PCT/GB2008/000952, filed Mar. 19, 2008, which claims the benefit of U.S. Provisional Patent Application No. 60/895,500, filed Mar. 19, 2007, both of which are hereby incorporated by reference in their entirety.

NAMES OF PARTIES TO A JOINT RESEARCH AGREEMENT

The subject matter claimed in this application was made as a result of activities undertaken within the scope of a joint research agreement dated Dec. 19, 2003, between AstraZeneca AB and Sumitomo Pharmaceuticals Co., Ltd. All of the rights and obligations of Sumitomo Pharmaceuticals Co., Ltd. as defined in the joint research agreement between AstraZeneca AB and Sumitomo Pharmaceuticals Co., Ltd. were assumed by Dainippon Sumitomo Pharma Co., Ltd., a company created by the merger of Dainippon Pharmaceuticals Co., Ltd. and Sumitomo Pharmaceuticals Co., Ltd. effective Oct. 3, 2005.

The present invention relates to adenine derivatives, processes for their preparation, pharmaceutical compositions containing them and their use in therapy.

The immune system is comprised of innate and acquired immunity, both of which work cooperatively to protect the host from microbial infections. It has been shown that innate immunity can recognize conserved pathogen-associated molecular patterns through toll-like receptors (TLRs) expressed on the cell surface of immune cells. Recognition of invading pathogens then triggers cytokine production (including interferon alpha(IFNα)) and upregulation of co-stimulatory molecules on phagocytes, leading to modulation of T cell function. Thus, innate immunity is closely linked to acquired immunity and can influence the development and regulation of an acquired response.

TLRs are a family of type I transmembrane receptors characterized by an NH₂-terminal extracellular leucine-rich repeat domain (LRR) and a COOH-terminal intracellular tail containing a conserved region called the Toll/IL-1 receptor (TIR) homology domain. The extracellular domain contains a varying number of LRR, which are thought to be involved in ligand binding. Eleven TLRs have been described to date in humans and mice. They differ from each other in ligand specificities, expression patterns, and in the target genes they can induce.

Ligands which act via TLRs (also known as immune response modifiers (IRMS)) have been developed, for example, the imidazoquinoline derivatives described in U.S. Pat. No. 4,689,338 which include the product Imiquimod for treating genital warts, and the adenine derivatives described in WO 98/01448 and WO 99/28321.

This patent application describes a class of 9-substituted-8-oxoadenine compounds having immuno-modulating properties which act via TLR7 that are useful in the treatment of viral or allergic diseases and cancers.

In accordance with the present invention, there is therefore provided a compound of formula

wherein

-   -   R¹ represents hydrogen, hydroxyl, or a C₁-C₆ alkoxy, C₂-C₅         alkoxycarbonyl, C₁-C₆ haloalkyl, C₁-C₆ haloalkoxy, C₆-C₁₀ aryl,         C₅-C₁₀ heteroaryl or C₃-C₈ cycloalkyl group, each group being         optionally substituted by one or more substituents independently         selected from halogen, hydroxyl, C₁-C₆ alkyl, C₁-C₆ haloalkyl,         C₁-C₆ alkoxy, C₁-C₆ haloalkoxy, C₂-C₅ alkoxycarbonyl, amino         (NH₂), (mono)-C₁-C₆ alkylamino and (di)-C₁-C₆ alkylamino;     -   Y¹ represents a single bond or C₁-C₆ alkylene;     -   X¹ represents a single bond, an oxygen or sulphur atom,         sulphonyl (SO₂) or NR³;     -   Z¹ represents a C₂-C₆ alkylene or C₃-C₈ cycloalkylene group,         each group being optionally substituted by at least one         hydroxyl;     -   X² represents NR⁴;     -   Y² represents a single bond or C₁-C₆ alkylene;     -   n is an integer 0, 1 or 2;     -   each R² group independently represents halogen, cyano,         S(O)_(m)R⁹, OR¹⁰, SO₂NR¹⁰R¹¹, CONR¹⁰R¹¹, NR¹⁰R¹¹, NR¹⁰SO₂R⁹,         NR¹⁰CO₂R⁹, NR¹⁰COR⁹, C₆-C₁₀ aryl, C₅-C₁₀ heteroaryl, C₁-C₆         alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl or C₃-C₈ cycloalkyl, the         latter six groups being optionally substituted by one or more         substituents independently selected from halogen, cyano,         S(O)_(p)R¹², OR¹³, SO₂NR¹³R¹⁴, CONR¹³R¹⁴, NR¹³R¹⁴, NR¹³SO₂R¹²,         NR¹³CO₂R¹², NR¹³COR¹², C₁-C₆ alkyl, C₁-C₃ haloalkyl and C₃-C₈         cycloalkyl;     -   R³ represents hydrogen or C₁-C₆ alkyl;     -   R⁴ represents CO₂R⁵, SO₂R⁵, COR⁵, SO₂NR⁶R⁷ or CONR⁶R⁷;     -   R⁵ represents         (i) a 3- to 8-membered saturated heterocyclic ring containing 1         or 2 ring heterogroups independently selected from NR⁸, S(O)_(q)         or oxygen, the ring being optionally substituted by one or more         substituents independently selected from halogen, hydroxyl,         C₁-C₆ alkyl and C₁-C₆ alkoxy, or         (ii) a C₆-C₁₀ aryl or C₅-C₁₀ heteroaryl group, each of which may         be optionally substituted by one or more substituents         independently selected from halogen, cyano, C₁-C₆ alkyl, C₁-C₃         haloalkyl, S(O)_(r)R⁹, OR¹⁰, CO₂R¹⁰, SO₂NR¹⁰R¹¹, CONR¹⁰R¹¹,         NR¹⁰R¹¹, NR¹⁰SO₂R⁹, NR¹⁰CO₂R⁹ and NR¹⁰COR⁹, or         (iii) a C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl or C₃-C₈         cycloalkyl group, each of which may be optionally substituted by         one or more substituents independently selected from halogen,         cyano, C₃-C₈ cycloalkyl, S(O)_(t)R¹², OR¹³, COR¹³, CO₂R¹³,         SO₂NR¹³R¹⁴, CONR¹³R¹⁴, NR⁶R⁷, NR¹³SO₂R¹², NR¹³CO₂R¹², NR¹³COR¹²,         C₆-C₁₀ aryl and C₅-C₁₀ heteroaryl, the latter two substituents         themselves being optionally substituted by one or more         substituents independently selected from C₁-C₆ alkyl, halogen,         hydroxy, methylsulphonyl and cyano;     -   R⁶ represents a hydrogen atom or a group selected from C₁-C₆         alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₈ cycloalkyl group and         a heterocyclic moiety, which group may be optionally substituted         by one or more substituents independently selected from halogen,         hydroxyl, oxo, cyano, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl,         C₃-C₈ cycloalkyl, OR¹⁵, S(O)_(v)R¹⁵, CO₂R¹⁶, COR¹⁶, NR¹⁶R¹⁷,         CONR¹⁶R¹⁷, NR¹⁶COR¹⁷, NR¹⁶CO₂R¹⁵, SO₂NR¹⁶R¹⁷, NR¹⁶SO₂R¹⁵, C₆-C₁₀         aryl, C₅-C₁₀ heteroaryl and a heterocyclic moiety, the latter         three substituents themselves being optionally substituted by         one or more substituents independently selected from C₁-C₆         alkyl, C₃-C₈ cycloalkyl, halogen, S(O)_(w)R¹⁵, CO₂R¹⁶, COR¹⁶,         hydroxy and cyano, and     -   R⁷ represents a hydrogen atom or a C₁-C₆ alkyl, C₂-C₆ alkenyl,         C₂-C₆ alkynyl or C₃-C₈ cycloalkyl group, each group being         optionally substituted by one or more substituents independently         selected from halogen, C₃-C₈ cycloalkyl, C₆-C₁₀ aryl, C₅-C₁₀         heteroaryl, carboxy, cyano, OR¹⁵, hydroxy and NR¹⁸R¹⁹, or     -   R⁶ and R⁷ together with the nitrogen atom to which they are         attached form a 3- to 8-membered saturated or partially         saturated heterocyclic ring optionally containing a further ring         heterogroup selected from nitrogen, S(O)_(x) and oxygen, the         heterocyclic ring being optionally substituted by one or more         substituents independently selected from halogen, hydroxyl,         carboxyl, cyano, OR²⁰, NR²¹R²², S(O)_(y)R²³, COR²⁴, CO₂R²⁴,         NR²⁴R²⁵, CONR²⁴R²⁵, NR²⁴COR²⁵, NR²⁴CO₂R²³, SO₂NR²⁴R²⁵,         NR²⁴SO₂R²³, C₆-C₁₀ aryl, benzyl, C₅-C₁₀ heteroaryl, a         heterocyclic moiety, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl         and C₃-C₈ cycloalkyl, the latter eight substituents themselves         being optionally substituted by one or more substituents         independently selected from halogen, oxo, cyano, OR²¹,         S(O)_(z)R²³, COR²⁴, COR²⁴ and NR²⁴R²⁵;     -   each R⁸, R¹⁰, R¹¹, R¹³, R¹⁴, R¹⁶, R¹⁷, R¹⁸, R¹⁹, R²¹, R²², R²⁴         and R²⁵ independently represents a hydrogen atom or a C₁-C₆         alkyl or C₃-C₆ cycloalkyl group;     -   each R⁹, R¹², R¹⁵ and R²³ independently represents C₁-C₆ alkyl         or C₃-C₆ cycloalkyl;     -   R²⁰ represents a C₁-C₆ alkyl group optionally substituted by one         or more substituents independently selected from halogen,         hydroxyl and OR²³;     -   m, p, q, r, t, v, w, x, y and z each independently represent an         integer 0, 1 or 2; and     -   A represents a C₆-C₁₀ aryl or C₅-C₁₂ heteroaryl group;         or a pharmaceutically acceptable salt thereof.

The compounds of the present invention are effective as TLR7 agonists and may, additionally, possess properties such as low toxicity, good selectivity and/or good metabolic stability which are advantageous for pharmaceutical compounds.

In the context of the present specification, unless otherwise stated, an alkyl, alkenyl or alkynyl substituent group or an alkyl, alkenyl or alkynyl moiety in a substituent group may be linear or branched. Examples of C₁-C₆ alkyl groups/moieties include methyl, ethyl, propyl, 2-methyl-1-propyl, 2-methyl-2-propyl, 2-methyl-1-butyl, 3-methyl-1-butyl, 2-methyl-3-butyl, 2,2-dimethyl-1-propyl, 2-methyl-pentyl, 3-methyl-1-pentyl, 4-methyl-1-pentyl, 2-methyl-2-pentyl, 3-methyl-2-pentyl, 4-methyl-2-pentyl, 2,2-dimethyl-1-butyl, 3,3-dimethyl-1-butyl, 2-ethyl-1-butyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl and n-hexyl. Examples of C₂-C₆ alkenyl and C₂-C₆ alkynyl groups/moieties include ethenyl, propenyl, 1-butenyl, 2-butenyl, 1-pentenyl, 1-hexenyl, 1,3-butadienyl, 1,3-pentadienyl, 1,4-pentadienyl, 1-hexadienyl, ethynyl, propynyl, 1-butynyl, 2-butynyl, 1-pentynyl and 1-hexynyl. Similarly, an alkylene group/moiety may be linear or branched. Examples of C₁-C₆ alkylene groups/moieties include methylene, ethylene, n-propylene, n-butylene, n-pentylene, n-hexylene, 1-methylethylene, 2-methylethylene, 1,2-dimethylethylene, 1-ethylethylene, 2-ethylethylene, 1-, 2- or 3-methylpropylene and 1-, 2- or 3-ethylpropylene. A C₁-C₆ haloalkyl or C₁-C₆ haloalkoxy substituent group/moiety will comprise at least one halogen atom, e.g. one, two, three, four or five halogen atoms, examples of which include trifluoromethyl, trifluoromethoxy or pentafluoroethyl. The alkyl groups in a di-C₁-C₆ alkylamino group/moiety may be the same as, or different from, one another. A C₆-C₁₀ aryl or C₅-C₁₂ heteroaryl substituent group/moiety may be monocyclic or polycyclic (e.g. bicyclic or tricyclic) in which the two or more rings are fused. The heteroaryl substituent group/moiety will comprise at least one ring heteroatom (e.g. one, two, three or four ring heteroatoms independently) selected from nitrogen, oxygen and sulphur. Examples of aryl and heteroaryl groups/moieties include phenyl, 1-naphthyl, 2-naphthyl, furyl, thienyl, pyrrolyl, pyridyl, indolyl, isoindolyl, quinolyl, isoquinolyl, pyrazolyl, imidazolyl, pyrimidinyl, pyrazinyl, pyridazinyl, thiazolyl and oxazolyl.

A heterocyclic moiety is defined as a saturated or partially saturated 3- to 8-membered ring containing at least one ring heterogroup selected from nitrogen, S(O)_(k) or oxygen (where k is 0, 1 or 2), which ring may be fused with a C₆-C₁₀ aryl or C₅-C₁₂ heteroaryl group as defined above. Examples of heterocyclic moieties include morpholine, azetidine, pyrrolidine, piperidine, piperazine, 3-pyrroline, isoindoline, tetrahydroquinoline and thiomorpholine. For the avoidance of doubt, it should be understood that the definitions of the heteroaryl groups and the heterocyclic moieties in formula (I) are not intended to include unstable structures or any O—O, O—S or S—S bonds and that a substituent, if present, may be attached to any suitable ring atom.

When any chemical moiety or group in formula (I) is described as being optionally substituted, it will be appreciated that the moiety or group may be either unsubstituted or substituted by one or more of the specified substituents. It will be appreciated that the number and nature of substituents will be selected so as to avoid sterically undesirable combinations.

In formula (I), R¹ represents hydrogen, hydroxyl, or a group selected from

C₁-C₆, preferably C₁-C₄, alkoxy (e.g. methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, tert-butoxy, n-pentoxy or n-hexoxy),

C₂-C₅ alkoxycarbonyl (e.g. ethoxycarbonyl, n-propoxycarbonyl, isopropoxycarbonyl, n-butoxycarbonyl, isobutoxycarbonyl, tert-butoxycarbonyl or n-pentoxycarbonyl),

C₁-C₆, preferably C₁-C₄, haloalkyl (e.g. trifluoromethyl or pentafluoroethyl),

C₁-C₆, preferably C₁-C₄, haloalkoxy (e.g. trifluoromethoxy),

C₆-C₁₀, preferably C₆, aryl (e.g. phenyl, indenyl, naphthyl or azulenyl),

C₅-C₁₀, preferably C₅-C₆, heteroaryl (e.g. pyridinyl, pyridazinyl, pyrazyl, triazinyl, indolyl, isoindolyl, quinolyl, isoquinolyl, pyrrolyl, pyrazolyl, imidazolyl, (1,2,3,)- and (1,2,4)-triazolyl, pyrazinyl, pyrimidinyl, tetrazolyl, furyl, thienyl, isoxazolyl, thiazolyl and oxazolyl) and C₃-C₈, preferably C₃-C₆, cycloalkyl (such as cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl), which group may be optionally substituted by one or more (e.g. one, two, three or four) substituents independently selected from halogen (e.g. chlorine, fluorine, bromine or iodine), hydroxyl, C₁-C₆, preferably C₁-C₄, alkyl (e.g. methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl or n-hexyl), C₁-C₆, preferably C₁-C₄, haloalkyl (e.g. trifluoromethyl or pentafluoroethyl), C₁-C₆, preferably C₁-C₄, alkoxy (e.g. methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, tert-butoxy, n-pentoxy or n-hexoxy), C₁-C₆, preferably C₁-C₄, haloalkoxy (e.g. trifluoromethoxy), C₂-C₅ alkoxycarbonyl (e.g. ethoxycarbonyl, n-propoxycarbonyl, isopropoxycarbonyl, n-butoxycarbonyl, isobutoxycarbonyl, tert-butoxycarbonyl or n-pentoxycarbonyl), amino, (mono)-C₁-C₆, preferably C alkylamino (e.g. methylamino, ethylamino, n-propylamino, isopropylamino, n-butylamino, isobutylamino, tert-butylamino, n-pentylamino or n-hexylamino) and (di)-C₁-C₆, preferably C₁-C₄, alkylamino (e.g. dimethylamino or diethylamino).

In an embodiment of the invention, R¹ represents hydrogen, hydroxyl, or a C₁-C₄ alkoxy, C₂-C₅ alkoxycarbonyl, C₁-C₄ haloalkyl, C₁-C₄ haloalkoxy, phenyl, C₅-C₆ heteroaryl or C₅-C₆ cycloalkyl group, each group being optionally substituted by one, two, three or four substituents independently selected from fluorine, chlorine, hydroxyl, C₁-C₄ alkyl, C₁-C₄ haloalkyl, C₁-C₄ alkoxy, C₁-C₄ haloalkoxy, C₂-C₅ alkoxycarbonyl, amino, (mono)-C₁-C₄ alkylamino and (di)-C₁-C₄ alkylamino.

In another embodiment, R¹ represents hydrogen.

Y¹ represents a single bond or C₁-C₆, preferably C₁-C₄, alkylene (such as methylene, ethylene, n-propylene, n-butylene, n-pentylene, n-hexylene, 1-methylethylene, 2-methylethylene, 1,2-dimethylethylene, 1-ethylethylene, 2-ethylethylene, 1-, 2- or 3-methylpropylene or 1-, 2- or 3-ethylpropylene).

In an embodiment of the invention, Y¹ represents C₁-C₆ alkylene.

In another embodiment, Y¹ represents C₄ alkylene, particularly n-butylene.

In an embodiment of the invention, X¹ represents oxygen.

In an embodiment of the invention, when X¹ represents oxygen, Y¹ represents C₁-C₆ alkylene and R¹ represents hydrogen.

Z¹ represents a C₂-C₆, preferably C₂-C₄, alkylene (e.g. ethylene, n-propylene, n-butylene, n-pentylene, n-hexylene, 1-methylethylene, 2-methylethylene, 1,2-dimethylethylene, 1-ethylethylene, 2-ethylethylene, 1-, 2- or 3-methylpropylene or 1-, 2- or 3-ethylpropylene) or C₃-C₈ cycloalkylene (e.g. cyclopropylene, cyclobutylene, cyclopentylene or cyclohexylene) group, each group being optionally substituted by at least one, e.g. one, two or three, hydroxyl groups.

In an embodiment of the invention, Z¹ represents C₂-C₆ alkylene, preferably C₃ alkylene (e.g. n-propylene).

X² represents NR⁴ where R⁴ represents CO₂R⁵, SO₂R⁵, COR⁵, SO₂NR⁶R⁷ or CONR⁶R⁷.

In an embodiment of the invention, R⁴ represents COR⁵.

Y² represents a single bond or C₁-C₆, preferably C₁-C₄, alkylene (such as methylene, ethylene, n-propylene, n-butylene, n-pentylene, n-hexylene, 1-methylethylene, 2-methylethylene, 1,2-dimethylethylene, 1-ethylethylene, 2-ethylethylene, 1-, 2- or 3-methylpropylene or 1-, 2- or 3-ethylpropylene).

In an embodiment of the invention, Y² represents C₁-C₆ alkylene, particularly methylene.

R⁵ represents

(i) a 3- to 8-, preferably 5- to 6-membered saturated heterocyclic ring containing 1 or 2 ring heterogroups independently selected from NR⁸, S(O)_(q) or oxygen, the ring being optionally substituted by one or more (e.g. one, two, three or four) substituents independently selected from halogen (e.g. fluorine, chlorine, bromine or iodine), hydroxyl, C₁-C₆, preferably C₁-C₄, alkyl (e.g. methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl or n-hexyl) and C₁-C₆, preferably C alkoxy (e.g. methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, tert-butoxy, n-pentoxy or n-hexoxy), or (ii) a C₆-C₁₀, preferably C₆, aryl or C₅-C₁₀, preferably C₅-C₆, heteroaryl group (examples of aryl and heteroaryl groups being the same as defined above for R¹), the aryl or heteroaryl group being optionally substituted by one or more (e.g. one, two, three or four) substituents independently selected from halogen (e.g. fluorine, chlorine, bromine or iodine), cyano, C₁-C₆, preferably C₁-C₄, alkyl (e.g. methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl or n-hexyl), C₁-C₃ haloalkyl (e.g. trifluoromethyl or pentafluoroethyl), S(O)_(r)R⁹, OR¹⁰, CO₂R¹⁰, SO₂NR¹⁰R¹¹, CONR¹⁰R¹¹, NR¹⁰R¹¹, NR¹⁰SO₂R⁹, NR¹⁰CO₂R⁹ and NR¹⁰COR⁹, or (iii) a group selected from C₁-C₆, preferably C₁-C₄, alkyl (e.g. methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl or n-hexyl), C₂-C₆, preferably C₂-C₄, alkenyl (e.g. ethenyl, propenyl, 1-butenyl, 2-butenyl, 1-pentenyl, 1-hexenyl, 1,3-butadienyl, 1,3-pentadienyl, 1,4-pentadienyl or 1-hexadienyl), C₂-C₆, preferably C₂-C₄, alkynyl (e.g. ethynyl, propynyl, 1-butynyl, 2-butynyl, 1-pentynyl or 1-hexynyl) and C₃-C₈, preferably C₃-C₆, cycloalkyl (e.g. cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl), which group may be optionally substituted by one or more (e.g. one, two, three or four) substituents independently selected from halogen (e.g. fluorine, chlorine, bromine or iodine), cyano, C₃-C₈, preferably C₃-C₆, cycloalkyl (e.g. cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl), S(O)_(t)R¹², OR¹³, COR¹³, CO₂R¹³, SO₂NR¹³R¹⁴, CONR¹³R¹⁴, NR⁶R⁷, NR¹³SO₂R¹², NR¹³CO₂R¹², NR¹³COR¹², C₆-C₁₀, preferably C₆, aryl and C₅-C₁₀, preferably C₅-C₆, heteroaryl, the latter two substituents themselves being optionally substituted by one or more (e.g. one, two, three or four) substituents independently selected from C₁-C₆, preferably C₁-C₄, alkyl (e.g. methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl or n-hexyl), halogen (e.g. fluorine, chlorine, bromine or iodine), hydroxy, methylsulphonyl and cyano.

In an embodiment of the invention, R⁵ represents a 5- to 6-membered saturated heterocyclic ring containing 1 or 2 ring heterogroups independently selected from NR⁸, S(O)_(q) or oxygen, the ring being optionally substituted by one, two, three or four substituents independently selected from fluorine, chlorine, hydroxyl, C₁-C₄ alkyl and C₁-C₄ alkoxy.

In another embodiment, R⁵ represents phenyl or C₅-C₆ heteroaryl, each of which may be optionally substituted by one, two, three or four substituents independently selected from fluorine, chlorine, cyano, C₁-C₄ alkyl, trifluoromethyl, S(O)_(r)R⁹, OR¹⁰, CO₂R¹⁰, SO₂NR¹⁰R¹¹, CONR¹⁰R¹¹, NR¹⁰R¹¹, NR¹⁰SO₂R⁹, NR¹⁰CO₂R⁹ and NR¹⁰COR⁹.

In yet another embodiment, R⁵ represents a group selected from C₁-C₄ alkyl, C₂-C₄ alkenyl, C₂-C₄ alkynyl and C₃-C₆ cycloalkyl, which group may be optionally substituted by one, two, three or four substituents independently selected from fluorine, chlorine, cyano, C₃-C₆ cycloalkyl, S(O)_(t)R¹², OR¹³, COR¹³, CO₂R¹³, SO₂NR¹³R¹⁴, CONR¹³R¹⁴, NR⁶R⁷, NR¹³SO₂R¹², NR¹³CO₂R¹², NR¹³COR¹², phenyl and C₅-C₆ heteroaryl, the latter two substituents themselves being optionally substituted by one, two, three or four substituents independently selected from C₁-C₄, alkyl, fluorine, chlorine, hydroxy, methylsulphonyl and cyano.

In a still further embodiment, R⁵ represents C₁-C₄ alkyl optionally substituted by one or two substituents independently selected from fluorine, chlorine, cyano, C₃-C₆ cycloalkyl, S(O)_(t)R¹², OR¹³, COR¹³, CO₂R¹³, SO₂NR¹³R¹⁴, CONR¹³R¹⁴, NR⁶R⁷, NR¹³SO₂R¹², NR¹³CO₂R¹², NR¹³COR¹², phenyl and C₅-C₆ heteroaryl, the latter two substituents themselves being optionally substituted by one, two, three or four substituents independently selected from C₁-C₄ alkyl, fluorine, chlorine, hydroxy, methylsulphonyl and cyano.

In another embodiment, R⁵ represents C₁-C₄ alkyl optionally substituted by one or two substituents independently selected from OR¹³, CO₂R¹³, CONR¹³R¹⁴, NR⁶R⁷, phenyl and C₅-C₆ heteroaryl, the latter two substituents themselves being optionally substituted by one, two, three or four substituents independently selected from C₁-C₄ alkyl and methylsulphonyl.

In a further embodiment, R⁵ represents C₁-C₄, preferably C₁-C₂, alkyl optionally substituted by one or two substituents independently selected from OR¹³, CO₂R¹³, CONR¹³R¹⁴, NR⁶R⁷, phenyl and C₅-C₆ heteroaryl (e.g. triazolyl or pyrazinyl), the latter two substituents themselves being optionally substituted by one or two substituents independently selected from C₁-C₄ alkyl (e.g. methyl) and methylsulphonyl.

In an embodiment of the invention, R⁶ represents a hydrogen atom or a group selected from

C₁-C₆, preferably C₁-C₄, alkyl (e.g. methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl or n-hexyl),

C₂-C₆, preferably C₂-C₄, alkenyl (e.g. ethenyl, propenyl, 1-butenyl, 2-butenyl, 1-pentenyl, 1-hexenyl, 1,3-butadienyl, 1,3-pentadienyl, 1,4-pentadienyl or 1-hexadienyl),

C₂-C₆, preferably C₂-C₄, alkynyl (e.g. ethynyl, propynyl, 1-butynyl, 2-butynyl, 1-pentynyl or 1-hexynyl),

C₃-C₈, preferably C₃-C₆, cycloalkyl (e.g. cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl), and

a heterocyclic moiety,

which group may be optionally substituted by one or more (e.g. one, two, three or four) substituents independently selected from halogen (e.g. fluorine, chlorine, bromine or iodine), hydroxyl, oxo, cyano, C₁-C₆, preferably C₁-C₄, alkyl, C₂-C₆, preferably C₂-C₄, alkenyl, C₂-C₆, preferably C₂-C₄, alkynyl, C₃-C₈, preferably C₃-C₆, cycloalkyl, OR¹⁵, S(O)_(v)R¹⁵, CO₂R¹⁶, COR¹⁶, NR¹⁶R¹⁷, CONR¹⁶R¹⁷, NR¹⁶COR¹⁷, NR¹⁶CO₂R¹⁵, SO₂NR¹⁶R¹⁷, NR¹⁶SO₂R¹⁵, C₆-C₁₀, preferably C₆, aryl, C₅-C₁₀, preferably C₅-C₆, heteroaryl and a heterocyclic moiety, the latter three substituents themselves being optionally substituted by one or more (e.g. one, two, three or four) substituents independently selected from C₁-C₆, preferably C₁-C₄, alkyl, C₃-C₈, preferably C₃-C₆, cycloalkyl, halogen (e.g. fluorine, chlorine, bromine or iodine), S(O)_(w)R¹⁵, CO₂R¹⁶, COR¹⁶, hydroxy and cyano; and R⁷ represents a hydrogen atom or a C₁-C₆, preferably C₁-C₄, alkyl (e.g. methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl or n-hexyl), C₂-C₆, preferably C₂-C₄, alkenyl (e.g. ethenyl, propenyl, 1-butenyl, 2-butenyl, 1-pentenyl, 1-hexenyl, 1,3-butadienyl, 1,3-pentadienyl, 1,4-pentadienyl or 1-hexadienyl), C₂-C₆, preferably C₂-C₄, alkynyl (e.g. ethynyl, propynyl, 1-butynyl, 2-butynyl, 1-pentynyl or 1-hexynyl), or C₃-C₈, preferably C₃-C₆, cycloalkyl (e.g. cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl) group, each group being optionally substituted by one or more (e.g. one, two, three or four) substituents independently selected from halogen (e.g. fluorine, chlorine, bromine or iodine), C₃-C₈, preferably C₃-C₆, cycloalkyl, C₆-C₁₀, preferably C₆, aryl, C₅-C₁₀, preferably C₅-C₆, heteroaryl, carboxy, cyano, OR¹⁵, hydroxy and NR¹⁸R¹⁹.

In an embodiment of the invention, R⁶ and R⁷ each represent a C₁-C₆, preferably C₁-C₄, alkyl group, e.g. methyl.

In an alternative embodiment of the invention, R⁶ and R⁷ together with the nitrogen atom to which they are attached form a 3- to 8-, preferably 5- to 6-membered saturated or partially saturated heterocyclic ring optionally containing a further ring heterogroup selected from nitrogen, S(O)_(x) and oxygen, the heterocyclic ring being optionally substituted by one or more (e.g. one, two, three or four) substituents independently selected from halogen (e.g. fluorine, chlorine, bromine or iodine), hydroxyl, carboxyl, cyano, OR²⁰, NR²¹R²², S(O)_(y)R²³, COR²⁴, CO₂R²⁴, NR²⁴R²⁵, CONR²⁴R²⁵, NR²⁴COR²⁵, NR²⁴CO₂R²³, SO₂NR²⁴R²⁵, NR²⁴SO₂R²³, C₆-C₁₀, preferably C₆, aryl, benzyl, C₅-C₁₀, preferably C₅-C₆, heteroaryl, a heterocyclic moiety, C₁-C₆, preferably C₁-C₄, alkyl, C₂-C₆, preferably C₂-C₄, alkenyl, C₂-C₆, preferably C₂-C₄, alkynyl and C₃-C₈, preferably C₃-C₆, cycloalkyl, the latter eight substituents themselves being optionally substituted by one or more (e.g. one, two, three or four) substituents independently selected from halogen (e.g. fluorine, chlorine, bromine or iodine), oxo, cyano, OR²¹, S(O)_(z)R²³, COR²⁴, CO₂R²⁴ and NR²⁴R²⁵.

In an embodiment of the invention, R⁶ and R⁷ together with the nitrogen atom to which they are attached form a 5- to 6-membered saturated heterocyclic ring optionally containing a further ring heterogroup selected from nitrogen, S(O)_(x) and oxygen, the heterocyclic ring being optionally substituted as defined above.

In another embodiment, R⁶ and R⁷ together with the nitrogen atom to which they are attached form a piperazinyl ring substituted by benzyl.

Each group R⁸, R¹⁰, R¹¹, R¹³, R¹⁴, R¹⁶, R¹⁷, R¹⁸, R¹⁹, R²¹, R²², R²⁴ and R²⁵ independently represents a hydrogen atom or a C₁-C₆, preferably C₁-C₄, alkyl (e.g. methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl or n-hexyl) or C₃-C₆, preferably C₅-C₆, cycloalkyl (i.e. cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl) group.

In an embodiment of the invention, each group R⁸, R¹⁰, R¹¹, R¹³, R¹⁴, R¹⁶, R¹⁷, R¹⁸, R¹⁹, R²¹, R²², R²⁴ and R²⁵ independently represents a hydrogen atom or a C₁-C₆, preferably C₁-C₄, alkyl group.

In another embodiment, each group R⁸, R¹⁰, R¹¹, R¹³, R¹⁴, R¹⁶, R¹⁷, R¹⁸, R¹⁹, R²¹, R²², R²⁴ and R²⁵ independently represents a C₁-C₄ alkyl group, particularly a methyl group.

Each group R⁹, R¹², R¹⁵ and R²³ independently represents C₁-C₆, preferably C₁-C₄, alkyl (e.g. methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl or n-hexyl) or C₃-C₆, preferably C₅-C₆, cycloalkyl (i.e. cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl).

In an embodiment of the invention, each group R⁹, R¹², R¹⁵ and R²³ independently represents a C₁-C₄ alkyl group, particularly a methyl group.

R²⁰ represents a C₁-C₆, preferably C₁-C₄, alkyl group (e.g. methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl or n-hexyl) optionally substituted by one or more (e.g. one, two, three or four) substituents independently selected from halogen (e.g. fluorine, chlorine, bromine or iodine), hydroxyl and OR²³.

A represents a C₆-C₁₀ aryl or C₅-C₁₂, preferably C₅-C₆, heteroaryl group.

In an embodiment of the invention, A represents a C₆-C₁₀ aryl group, e.g. phenyl.

In formula (I), n is an integer 0, 1 or 2.

When n is 1 or 2, each R² group independently represents halogen (e.g. fluorine, chlorine, bromine or iodine), cyano, S(O)_(m)R⁹, OR¹⁰, SO₂NR¹⁰R¹¹, CONR¹⁰R¹¹, NR¹⁰R¹¹, NR¹⁰SO₂R⁹, NR¹⁰CO₂R⁹, NR¹⁰COR⁹, C₆-C₁₀, preferably C₆, aryl, C₅-C₁₀, preferably C₅-C₆, heteroaryl, C₁-C₆, preferably C₁-C₄, alkyl, C₂-C₆, preferably C₂-C₄, alkenyl, C₂-C₆, preferably C₂-C₄, alkynyl or C₃-C₈, preferably C₃-C₆, cycloalkyl, the latter six groups being optionally substituted by one or more (e.g. one, two, three or four) substituents independently selected from halogen (e.g. fluorine, chlorine, bromine or iodine), cyano, S(O)_(p)R¹², OR¹³, SO₂NR¹³R¹⁴, CONR¹³R¹⁴, NR¹³R¹⁴, NR¹³SO₂R¹², NR¹³CO₂R¹², NR¹³COR¹², C₁-C₆, preferably C₁-C₄, alkyl, C₁-C₃ haloalkyl and C₃-C₈, preferably C₃-C₆, cycloalkyl.

In an embodiment of the invention, n is 0.

In an embodiment of the invention,

-   -   R¹ represents hydrogen;     -   Y¹ represents C₄ alkylene;     -   X¹ represents an oxygen atom;     -   Z¹ represents C₃ alkylene;     -   X² represents NR⁴;     -   Y² represents methylene;     -   n is 0;     -   R⁴ represents COR⁵;     -   R⁵ represents C₁-C₂ alkyl optionally substituted by one or two         substituents independently selected from OR¹³, CO₂R¹³,         CONR¹³R¹⁴, NR⁶R⁷, phenyl and C₅-C₆ heteroaryl, the latter two         substituents themselves being optionally substituted by one or         two substituents to independently selected from C₁-C₄ alkyl and         methylsulphonyl;     -   either R⁶ and R⁷ both represent C₁-C₄ alkyl, or R⁶ and R⁷         together with the nitrogen atom to which they are attached form         a piperazinyl ring substituted by benzyl;     -   each R¹³ and R¹⁴ independently represents C₁-C₄ alkyl; and     -   A represents C₆-C₁₀ aryl.

Examples of compounds of the invention include:

-   N-[3-(6-Amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl]-N-benzylacetamide, -   N-[3-(6-Amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl]-N-benzyl-2-methoxyacetamide, -   Methyl     4-[[3-(6-amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl](benzyl)amino]-4-oxobutanoate, -   N-[3-(6-Amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl]-N-benzyl-3-methoxypropanamide, -   N-[3-(6-Amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl]-N-benzyl-N′,N′-dimethylsuccinamide, -   N-[3-(6-Amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl]-N-benzyl-2-[4-(methylsulfonyl)phenyl]acetamide, -   N-[3-(6-Amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl]-N-benzyl-2-(4-benzylpiperazin-1-yl)acetamide, -   N-[3-(6-Amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl]-N-benzyl-2-(3,5-dimethyl-1H-1,2,4-triazol-1-yl)acetamide, -   N-[3-(6-Amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl]-N-benzyl-3-pyrazin-2-ylpropanamide,     and -   N-[3-(6-Amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl]-N-benzyl-N³,N³-dimethyl-β-alaninamide,     and their pharmaceutically acceptable salts.

It should be noted that each of the chemical compounds listed above represents a particular and independent aspect of the invention.

The present invention further provides a process for the preparation of a compound of formula (I) or a pharmaceutically acceptable salt thereof as defined above which comprises,

(a) when R⁴ represents a group COR⁵, reacting a compound of formula

wherein n, R¹, R², A, X¹, Y¹, Z¹ and Y² are as defined in formula (I), with a compound of formula (III), R¹⁵—C(O)-L¹, wherein L¹ represents halogen or hydroxy and R⁵ is as defined in formula (I), in the presence of a base or a coupling reagent as required; (b) when R⁴ represents a group COR⁵ and R⁵ represents a group C₁-C₆ alkyl-NR⁶R⁷, reacting a compound of formula

wherein R³⁰ represents a C₁-C₆ alkyl group, L² represents a leaving group (e.g. halogen, mesylate or triflate) and n, R¹, R², A, X¹, Y¹, Z¹ and Y² are as defined in formula (I), with a compound of formula (V), NHR⁶R⁷, wherein R⁶ and R⁷ are as defined in formula (I), in the presence of a base; (c) when R⁴ represents a group SO₂R⁵, reacting a compound of formula (II) as defined in (a) above with a compound of formula (VI), L³-S(O)₂—R⁵, wherein L³ represents a leaving group (e.g. halogen) and R⁵ is as defined in formula (I), in the presence of a base; (d) when R⁴ represents a group CO₂R⁵, reacting a compound of formula (II) as defined in (a) above with a compound of formula (VII), L⁴-C(O)—OR⁵, wherein L⁴ represents a leaving group (e.g. halogen) and R⁵ is as defined in formula (I), in the presence of a base; (e) when R⁴ represents a group SO₂NR⁶R⁷, reacting a compound of formula (II) as defined in (a) above with a compound of formula (VIII), L⁵-S(O)₂—NR⁶R⁷, wherein L⁵ represents a leaving group (e.g. halogen) and R⁶ and R⁷ are as defined in formula (I), in the presence of a base; or (f) when R⁴ represents a group CONR⁶R⁷, reacting a compound of formula (II) as defined in (a) above with a compound of formula (IX), L⁶-C(O)—NR⁶R⁷, wherein L⁶ represents a leaving group (e.g. halogen) and R⁶ and R⁷ are as defined in formula (I), in the presence of a base; and optionally thereafter carrying out one or more of the following procedures:

-   -   converting a compound of formula (I) into another compound of         formula (I),     -   removing any protecting groups,     -   forming a pharmaceutically acceptable salt.

In process (a) above, the reaction is conveniently carried out in an organic solvent such as dimethylformamide, dichloromethane, acetonitrile or N-methylpyrrolidone at a temperature in the range from 0° C. to 150° C. If L¹ in formula (III) represents a halogen atom, the reaction is carried out in the presence of a suitable base, examples of which include diisopropyl ethylamine, triethylamine and pyridine. If L¹ in formula (III) is hydroxy, then the reaction is carried out in the presence of a coupling reagent, suitable examples of which include benzotriazol-1-yloxytripyrrolidinophosphonium hexafluorophosphate (PyBop), N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide (EDC) and O-(7-azabenzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium hexafluorophosphate (HATU).

In process (b) above, the reaction is conveniently carried out in an organic solvent such as dimethylformamide, dimethylsulphoxide or acetonitrile at a temperature in the range from 0° C. to 150° C. Suitable bases include diisopropyl ethylamine, triethylamine and pyridine.

In each of processes (c), (d), (e) and (f) above, the reaction is conveniently carried out in an organic solvent such as dimethylformamide, dichloromethane or acetonitrile at a temperature in the range from 0° C. to 150° C. Suitable bases include diisopropyl ethylamine, triethylamine and pyridine.

Compounds of formula (II) may be prepared by treating a compound of formula

wherein n, R¹, R², A, X¹, Y¹, Z¹ and Y² are as defined in formula (II) with an acid. The reaction may be carried out in an organic solvent such as methanol, tetrahydrofuran or dioxane using either an inorganic acid such as hydrochloric acid, hydrobromic acid or sulfuric acid, or an organic acid such as trifluoroacetic acid.

Compounds of formula (X) in which Y² represents C₁-C₆ alkylene may be prepared by reacting a compound of formula

wherein R¹, X¹, Y¹ and Z¹ are as defined in formula (X), with a compound of formula

wherein Y³ represents a bond or a C₁-C₅ alkylene group and n, A and R² are as defined in formula (X). The reaction may be carried out in the presence of a suitable reducing agent (for example, sodium triacetoxyborohydride or sodium borohydride), in an organic solvent such as 1-methyl-2-pyrrolidinone, 1,2-dichloroethane, tetrahydrofuran or methanol at a temperature, for example, in the range from 0° C. to 150° C.

Compounds of formula (X) in which Y² represents a single bond may be prepared by reacting a compound of formula (XI) as defined above with a compound of formula

wherein L⁷ represents a leaving group such as halogen or mesylate and n, A and R² are as defined in formula (X), in the presence of a base. The reaction may be carried out in an organic solvent such as dimethylformamide, dioxane or acetonitrile at a temperature, for example, in the range from 25° C. to 150° C. Suitable bases include diisopropyl ethylamine, triethylamine and potassium carbonate.

Compounds of formula (XI) may be prepared by treating a compound of formula

wherein PG₁ represents a protecting group (e.g. phthalimide or Fmoc) and R¹, X¹, Y¹ and Z¹ are as defined in formula (XI) with hydrazine in ethanol or with an organic base such as piperidine.

Compounds of formula (XIV) may be prepared by reacting a compound of formula

wherein R¹, X¹ and Y¹ are as defined in formula (XIV) with a compound of formula (XVI), L⁸-Z¹—NH—PG₁, wherein L⁸ represents a leaving group (e.g. halogen, mesylate or triflate), and Z¹ and PG₁ are as defined in formula (XIV). The reaction may conveniently be carried out in an organic solvent such as dimethylformamide, dimethylsulphoxide or acetonitrile in the presence of a base such as an alkali metal carbonate (for example, sodium carbonate or potassium carbonate) or an alkaline earth metal carbonate (for example, calcium carbonate) or a metal hydroxide (for example, sodium hydroxide or potassium hydroxide), at a temperature, for example, in the range from 0° C. to 150° C., preferably at room temperature (20° C.).

Compounds of formula (XV) where X¹ represents an oxygen atom may be prepared as illustrated in the following reaction scheme:

The compound of formula (B) is prepared by reacting the compound of formula (A) with ammonia in an organic solvent such as methanol, ethanol, propanol, butanol, tetrahydrofuran, 1,4-dioxane, diglyme, acetonitrile or an aqueous mixture of any one of the preceding solvents. The reaction may be carried out in an autoclave and at a temperature, for example, in the range from 20° C. to 200° C.

Compounds of formula (C) may be prepared by reacting the compound of formula (B) with an alcohol of formula

wherein R¹ and Y¹ are as defined in formula (XV), in the presence of a base such as sodium hydride and in an organic solvent such as tetrahydrofuran, 1,4-dioxane, diglyme, N,N-dimethylformamide or dimethylsulfoxide, preferably at elevated temperature, e.g. at a temperature in the range from 20° C. to 150° C. Alternatively an alkali metal such as sodium may be dissolved in a C₁-C₆ alkanol and then reacted with the compound of formula (B), preferably at elevated temperature, e.g. at a temperature in the range from 20° C. to 150° C.

Compounds of formula (D) may be prepared by brominating a compound of formula (C). The reaction may be carried out using a brominating agent such as bromine, hydroperbromic acid or N-bromosuccinimide, in an organic solvent such as carbon tetrachloride, methylene chloride, dichloroethane, diethyl ether, acetic acid or carbon disulfide. The reaction temperature will generally be in the range from 0° C. to the boiling point of the solvent.

Compounds of formula (E) are prepared by reacting a compound of formula (D) with sodium methoxide in an organic solvent such as methanol and at a temperature, for example, in the range from 20° C. to 150° C.

Compounds of formula (F) may be obtained by treating a compound of formula (E) with an acid such as trifluoroacetic acid in an organic solvent such as methanol.

Other compounds of formula (XV) may be prepared by processes known in the art.

Compounds of formula (IV) may be prepared by reacting a compound of formula (II) with a compound of formula (XVIII), HO—C(O)—R³⁰-L², wherein R³⁰ and L² are as defined in formula (IV) under similar reaction conditions to those used in process (a) above.

Compounds of formulae (III), (V), (VI), (VII), (VIII), (IX), (XII), (XIII), (XVI), (XVII) and (XVIII) are either commercially available, are well known in the literature or may be prepared easily using known techniques.

It will be appreciated by those skilled in the art that in the processes of the present invention certain functional groups such as hydroxyl or amino groups in the reagents may need to be protected by protecting groups. Thus, the preparation of the compounds of formula (I) may involve, at an appropriate stage, the removal of one or more protecting groups.

The protection and deprotection of functional groups is described in ‘Protective Groups in Organic Chemistry’, edited by J. W. F. McOmie, Plenum Press (1973) and ‘Protective Groups in Organic Synthesis’, 3^(rd) edition, T. W. Greene and P. G. M. Wuts, Wiley-Interscience (1999).

The compounds of formula (I) above may be converted to a pharmaceutically acceptable salt thereof, preferably an acid addition salt such as a hydrochloride, hydrobromide, trifluoroacetate, sulphate, phosphate, acetate, fumarate, maleate, tartrate, lactate, citrate, pyruvate, succinate, oxalate, methanesulphonate or p-toluenesulphonate.

Compounds of formula (I) are capable of existing in stereoisomeric forms. It will be understood that the invention encompasses the use of all geometric and optical isomers (including atropisomers) of the compounds of formula (I) and mixtures thereof including racemates. The use of tautomers and mixtures thereof also form an aspect of the present invention. Enantiomerically pure forms are particularly desired.

The compounds of formula (I) and their pharmaceutically acceptable salts have activity as pharmaceuticals, in particular as modulators of toll-like receptor (especially TLR7) activity, and thus may be used in the treatment of:

1. respiratory tract: obstructive diseases of the airways including: asthma, including bronchial, allergic, intrinsic, extrinsic, exercise-induced, drug-induced (including aspirin and NSAID-induced) and dust-induced asthma, both intermittent and persistent and of all severities, and other causes of airway hyper-responsiveness; chronic obstructive pulmonary disease (COPD); bronchitis, including infectious and eosinophilic bronchitis; emphysema; bronchiectasis; cystic fibrosis; sarcoidosis; farmer's lung and related diseases; hypersensitivity pneumonitis; lung fibrosis, including cryptogenic fibrosing alveolitis, idiopathic interstitial pneumonias, fibrosis complicating anti-neoplastic therapy and chronic infection, including tuberculosis and aspergillosis and other fungal infections; complications of lung transplantation; vasculitic and thrombotic disorders of the lung vasculature, and pulmonary hypertension; antitussive activity including treatment of chronic cough associated with inflammatory and secretory conditions of the airways, and iatrogenic cough; acute and chronic rhinitis including rhinitis medicamentosa, and vasomotor rhinitis; perennial and seasonal allergic rhinitis including rhinitis nervosa (hay fever); nasal polyposis; acute viral infection including the common cold, and infection due to respiratory syncytial virus, influenza, coronavirus (including SARS) and adenovirus; 2. skin: psoriasis, atopic dermatitis, contact dermatitis or other eczematous dermatoses, and to delayed-type hypersensitivity reactions; phyto- and photodermatitis; seborrhoeic dermatitis, dermatitis herpetiformis, lichen planus, lichen sclerosus et atrophica, pyoderma gangrenosum, skin sarcoid, discoid lupus erythematosus, pemphigus, pemphigoid, epidermolysis bullosa, urticaria, angioedema, vasculitides, toxic erythemas, cutaneous eosinophilias, alopecia areata, male-pattern baldness, Sweet's syndrome, Weber-Christian syndrome, erythema multiforme; cellulitis, both infective and non-infective; panniculitis; cutaneous lymphomas, non-melanoma skin cancer and other dysplastic lesions; drug-induced disorders including fixed drug eruptions; 3. eyes: blepharitis; conjunctivitis, including perennial and vernal allergic conjunctivitis; iritis; anterior and posterior uveitis; choroiditis; autoimmune, degenerative or inflammatory disorders affecting the retina; ophthalmitis including sympathetic ophthalmitis; sarcoidosis; infections including viral, fungal, and bacterial; 4. genitourinary: nephritis including interstitial and glomerulonephritis; nephrotic syndrome; cystitis including acute and chronic (interstitial) cystitis and Hunner's ulcer; acute and chronic urethritis, prostatitis, epididymitis, oophoritis and salpingitis; vulvo-vaginitis; Peyronie's disease; erectile dysfunction (both male and female); 5. allograft rejection: acute and chronic following, for example, transplantation of kidney, heart, liver, lung, bone marrow, skin or cornea or following blood transfusion; or chronic graft versus host disease; 6. other auto-immune and allergic disorders including rheumatoid arthritis, irritable bowel syndrome, systemic lupus erythematosus, multiple sclerosis, Hashimoto's thyroiditis, Graves' disease, Addison's disease, diabetes mellitus, idiopathic thrombocytopaenic purpura, eosinophilic fasciitis, hyper-IgE syndrome, antiphospholipid syndrome and Sazary syndrome; 7. oncology: treatment of common cancers including prostate, breast, lung, ovarian, pancreatic, bowel and colon, stomach, skin and brain tumors and malignancies affecting the bone marrow (including the leukaemias) and lymphoproliferative systems, such as Hodgkin's and non-Hodgkin's lymphoma; including the prevention and treatment of metastatic disease and tumour recurrences, and paraneoplastic syndromes; and, 8. infectious diseases: virus diseases such as genital warts, common warts, plantar warts, hepatitis B, hepatitis C, herpes simplex virus, molluscum contagiosum, variola, human immunodeficiency virus (HIV), human papilloma virus (HPV), cytomegalovirus (CMV), varicella zoster virus (VZV), rhinovirus, adenovirus, coronavirus, influenza, para-influenza; bacterial diseases such as tuberculosis and mycobacterium avium, leprosy; other infectious diseases, such as fungal diseases, chlamydia, candida, aspergillus, cryptococcal meningitis, pneumocystis carnii, cryptosporidiosis, histoplasmosis, toxoplasmosis, trypanosome infection and leishmaniasis.

Thus, the present invention provides a compound of formula (I) or a pharmaceutically-acceptable salt thereof as hereinbefore defined for use in therapy.

In a further aspect, the present invention provides the use of a compound of formula (I) or a pharmaceutically acceptable salt thereof as hereinbefore defined in the manufacture of a medicament for use in therapy.

In the context of the present specification, the term “therapy” also includes “prophylaxis” unless there are specific indications to the contrary. The terms “therapeutic” and “therapeutically” should be construed accordingly.

Prophylaxis is expected to be particularly relevant to the treatment of persons who have suffered a previous episode of, or are otherwise considered to be at increased risk of, the disease or condition in question. Persons at risk of developing a particular disease or condition generally include those having a family history of the disease or condition, or those who have been identified by genetic testing or screening to be particularly susceptible to developing the disease or condition.

In particular, the compounds of the invention (including pharmaceutically acceptable salts) may be used in the treatment of asthma, COPD, allergic rhinitis, allergic conjunctivitis, atopic dermatitis, cancer, hepatitis B, hepatitis C, HIV, HPV, bacterial infections and dermatosis.

The invention still further provides a method of treating, or reducing the risk of, a disease or condition comprising or arising from abnormal cell growth (e.g. a cancer), which method comprises administering to a patient in need thereof a therapeutically effective amount of a compound of formula (I) or a pharmaceutically acceptable salt thereof as hereinbefore defined.

The invention also provides a method of treating, or reducing the risk of, an obstructive airways disease or condition (e.g. asthma or COPD) which comprises administering to a patient in need thereof a therapeutically effective amount of a compound of formula (I) or a pharmaceutically acceptable salt thereof as hereinbefore defined.

For the above-mentioned therapeutic uses the dosage administered will, of course, vary with the compound employed, the mode of administration, the treatment desired and the disorder indicated. For example, the daily dosage of the compound of the invention, if inhaled, may be in the range from 0.05 micrograms per kilogram body weight (μg/kg) to 100 micrograms per kilogram body weight (μg/kg). Alternatively, if the compound is administered orally, then the daily dosage of the compound of the invention may be in the range from 0.01 micrograms per kilogram body weight (μg/kg) to 100 milligrams per kilogram body weight (mg/kg).

The compounds of formula (I) and pharmaceutically acceptable salts thereof may be used on their own but will generally be administered in the form of a pharmaceutical composition in which the formula (I) compound/salt (active ingredient) is in association with a pharmaceutically acceptable adjuvant, diluent or carrier. Conventional procedures for the selection and preparation of suitable pharmaceutical formulations are described in, for example, “Pharmaceuticals—The Science of Dosage Form Designs”, M. E. Aulton, Churchill Livingstone, 1988.

Depending on the mode of administration, the pharmaceutical composition will preferably comprise from 0.05 to 99% w (percent by weight), more preferably from 0.05 to 80% w, still more preferably from 0.10 to 70% w, and even more preferably from 0.10 to 50% w, of active ingredient, all percentages by weight being based on total composition.

The present invention also provides a pharmaceutical composition comprising a compound of formula (I) or a pharmaceutically acceptable salt thereof as hereinbefore defined, in association with a pharmaceutically acceptable adjuvant, diluent or carrier.

The invention further provides a process for the preparation of a pharmaceutical composition of the invention which comprises mixing a compound of formula (I) or a pharmaceutically acceptable salt thereof as hereinbefore defined with a pharmaceutically acceptable adjuvant, diluent or carrier.

The pharmaceutical compositions may be administered topically (e.g. to the skin or to the lung and/or airways) in the form, e.g., of creams, solutions, suspensions, heptafluoroalkane (HFA) aerosols and dry powder formulations, for example, formulations in the inhaler device known as the Turbuhaler®; or systemically, e.g. by oral administration in the form of tablets, capsules, syrups, powders or granules; or by parenteral administration in the form of a sterile solution, suspension or emulsion for injection (including intravenous, subcutaneous, intramuscular, intravascular or infusion); or by rectal administration in the form of suppositories.

Dry powder formulations and pressurized HFA aerosols of the compounds of the invention (including pharmaceutically acceptable salts) may be administered by oral or nasal inhalation. For inhalation, the compound is desirably finely divided. The finely divided compound preferably has a mass median diameter of less than 10 micrometres (μm), and may be suspended in a propellant mixture with the assistance of a dispersant, such as a C₈-C₂₀ fatty acid or salt thereof, (for example, oleic acid), a bile salt, a phospholipid, an alkyl saccharide, a perfluorinated or polyethoxylated surfactant, or other pharmaceutically acceptable dispersant. The compounds of the invention may also be administered by means of a dry powder inhaler. The inhaler may be a single or a multi dose inhaler, and may be a breath actuated dry powder inhaler.

One possibility is to mix the finely divided compound of the invention with a carrier substance, for example, a mono-, di- or polysaccharide, a sugar alcohol, or another polyol. Suitable carriers are sugars, for example, lactose, glucose, raffinose, melezitose, lactitol, maltitol, trehalose, sucrose, mannitol; and starch. Alternatively the finely divided compound may be coated by another substance. The powder mixture may also be dispensed into hard gelatine capsules, each containing the desired dose of the active compound.

Another possibility is to process the finely divided powder into spheres which break up during the inhalation procedure. This spheronized powder may be filled into the drug reservoir of a multidose inhaler, for example, that known as the Turbuhaler® in which a dosing unit meters the desired dose which is then inhaled by the patient. With this system the active ingredient, with or without a carrier substance, is delivered to the patient.

For oral administration the compound of the invention may be admixed with an adjuvant or a carrier, for example, lactose, saccharose, sorbitol, mannitol; a starch, for example, potato starch, corn starch or amylopectin; a cellulose derivative; a binder, for example, gelatine or polyvinylpyrrolidone; and/or a lubricant, for example, magnesium stearate, calcium stearate, polyethylene glycol, a wax, paraffin, and the like, and then compressed into tablets. If coated tablets are required, the cores, prepared as described above, may be coated with a concentrated sugar solution which may contain, for example, gum arabic, gelatine, talcum and titanium dioxide. Alternatively, the tablet may be coated with a suitable polymer dissolved in a readily volatile organic solvent.

For the preparation of soft gelatine capsules, the compound of the invention may be admixed with, for example, a vegetable oil or polyethylene glycol. Hard gelatine capsules may contain granules of the compound using either the above-mentioned excipients for tablets. Also liquid or semisolid formulations of the compound of the invention may be filled into hard gelatine capsules.

Liquid preparations for oral application may be in the form of syrups or suspensions, for example, solutions containing the compound of the invention, the balance being sugar and a mixture of ethanol, water, glycerol and propylene glycol. Optionally such liquid preparations may contain colouring agents, flavouring agents, saccharine and/or carboxymethylcellulose as a thickening agent or other excipients known to those skilled in art.

The compounds of the invention (that is, compounds of formula (I) and pharmaceutically acceptable salts thereof) may also be administered in conjunction with other compounds used for the treatment of the above conditions.

The invention therefore further relates to combination therapies wherein a compound of the invention or a pharmaceutical composition or formulation comprising a compound of the invention is administered concurrently or sequentially or as a combined preparation with another therapeutic agent or agents, for the treatment of one or more of the conditions listed.

The anti-cancer treatment defined hereinbefore may be applied as a sole therapy or may involve, in addition to the compound of the invention, conventional surgery or radiotherapy or chemotherapy. Such chemotherapy may include one or more of the following categories of anti-tumour agents:—

(i) other antiproliferative/antineoplastic drugs and combinations thereof, as used in medical oncology, such as alkylating agents (for example cis-platin, oxaliplatin, carboplatin, cyclophosphamide, nitrogen mustard, melphalan, chlorambucil, busulphan, temozolamide and nitrosoureas); antimetabolites (for example gemcitabine and antifolates such as fluoropyrimidines like 5-fluorouracil and tegafur, raltitrexed, methotrexate, cytosine arabinoside, and hydroxyurea); antitumour antibiotics (for example anthracyclines like adriamycin, bleomycin, doxorubicin, daunomycin, epirubicin, idarubicin, mitomycin-C, dactinomycin and mithramycin); antimitotic agents (for example vinca alkaloids like vincristine, vinblastine, vindesine and vinorelbine and taxoids like taxol and taxotere and polokinase inhibitors); and topoisomerase inhibitors (for example epipodophyllotoxins like etoposide and teniposide, amsacrine, topotecan and camptothecin); (ii) cytostatic agents such as antioestrogens (for example tamoxifen, fulvestrant, toremifene, raloxifene, droloxifene and iodoxyfene), antiandrogens (for example bicalutamide, flutamide, nilutamide and cyproterone acetate), LHRH antagonists or LHRH agonists (for example goserelin, leuprorelin and buserelin), progestogens (for example megestrol acetate), aromatase inhibitors (for example as anastrozole, letrozole, vorazole and exemestane) and inhibitors of 5α-reductase such as finasteride; (iii) anti-invasion agents (for example c-Src kinase family inhibitors like 4-(6-chloro-2,3-methylenedioxyanilino)-7-[2-(4-methylpiperazin-1-yl)ethoxy]-5-tetrahydropyran-4-yloxyquinazoline (AZD0530; International Patent Application WO 01/94341) and N-(2-chloro-6-methylphenyl)-2-{6-[4-(2-hydroxyethyl)piperazin-1-yl]-2-methylpyrimidin-4-ylamino}thiazole-5-carboxamide (dasatinib, BMS-354825; J. Med. Chem., 2004, 47, 6658-6661), and metalloproteinase inhibitors like marimastat, inhibitors of urokinase plasminogen activator receptor function or antibodies to Heparanase); (iv) inhibitors of growth factor function: for example such inhibitors include growth factor antibodies and growth factor receptor antibodies (for example the anti-erbB2 antibody trastuzumab [Herceptin™], the anti-EGFR antibody panitumumab, the anti-erbB1 antibody cetuximab [Erbitux®, C225] and any growth factor or growth factor receptor antibodies disclosed by Stern et al. Critical reviews in oncology/haematology, 2005, Vol. 54, pp 11-29); such inhibitors also include tyrosine kinase inhibitors, for example inhibitors of the epidermal growth factor family (for example EGFR family tyrosine kinase inhibitors such as N-(3-chloro-4-fluorophenyl)-7-methoxy-6-(3-morpholinopropoxy)quinazolin-4-amine (gefitinib, ZD1839), N-(3-ethynylphenyl)-6,7-bis(2-methoxyethoxy)quinazolin-4-amine (erlotinib, OSI-774) and 6-acrylamido-N-(3-chloro-4-fluorophenyl)-7-(3-morpholinopropoxy)-quinazolin-4-amine (CI 1033), erbB2 tyrosine kinase inhibitors such as lapatinib, inhibitors of the hepatocyte growth factor family, inhibitors of the platelet-derived growth factor family such as imatinib, inhibitors of serine/threonine kinases (for example Ras/Raf signalling inhibitors such as farnesyl transferase inhibitors, for example sorafenib (BAY 43-9006)), inhibitors of cell signalling through MEK and/or AKT kinases, inhibitors of the hepatocyte growth factor family, c-kit inhibitors, abl kinase inhibitors, IGF receptor (insulin-like growth factor) kinase inhibitors; aurora kinase inhibitors (for example AZD1152, PH739358, VX-680, MLN8054, R763, MP235, MP529, VX-528 AND AX39459) and cyclin dependent kinase inhibitors such as CDK2 and/or CDK4 inhibitors; (v) antiangiogenic agents such as those which inhibit the effects of vascular endothelial growth factor, [for example the anti-vascular endothelial cell growth factor antibody bevacizumab (Avastin™) and VEGF receptor tyrosine kinase inhibitors such as 4-(4-bromo-2-fluoroanilino)-6-methoxy-7-(1-methylpiperidin-4-ylmethoxy)quinazoline (ZD6474; Example 2 within WO 01/32651), 4-(4-fluoro-2-methylindol-5-yloxy)-6-methoxy-7-(3-pyrrolidin-1-ylpropoxy)quinazoline (AZD2171; Example 240 within WO 00/47212), vatalanib (PTK787; WO 98/35985) and SU11248 (sunitinib; WO 01/60814), compounds such as those disclosed in International Patent Applications WO97/22596, WO 97/30035, WO 97/32856 and WO 98/13354 and compounds that work by other mechanisms (for example linomide, inhibitors of integrin αvβ3 function and angiostatin)]; (vi) vascular damaging agents such as Combretastatin A4 and compounds disclosed in International Patent Applications WO 99/02166, WO 00/40529, WO 00/41669, WO 01/92224, WO 02/04434 and WO 02/08213; (vii) antisense therapies, for example those which are directed to the targets listed above, such as ISIS 2503, an anti-ras antisense; (viii) gene therapy approaches, including for example approaches to replace aberrant genes such as aberrant p53 or aberrant BRCA1 or BRCA2, GDEPT (gene-directed enzyme pro-drug therapy) approaches such as those using cytosine deaminase, thymidine kinase or a bacterial nitroreductase enzyme and approaches to increase patient tolerance to chemotherapy or radiotherapy such as multi-drug resistance gene therapy; and (ix) immunotherapy approaches, including for example ex-vivo and in-vivo approaches to increase the immunogenicity of patient tumour cells, such as transfection with cytokines such as interleukin 2, interleukin 4 or granulocyte-macrophage colony stimulating factor, approaches to decrease T-cell anergy, approaches using transfected immune cells such as cytokine-transfected dendritic cells, approaches using cytokine-transfected tumour cell lines and approaches using anti-idiotypic antibodies.

Furthermore, for the treatment of the inflammatory diseases COPD, asthma and allergic rhinitis the compounds of the invention may be combined with agents such as tumour necrosis factor alpha (TNF-alpha) inhibitors such as anti-TNF monoclonal antibodies (for example infliximab [Remicade®], CDP-870 and adalimumab) and TNF receptor immunoglobulin molecules (such as entanercept [Enbrel®]); non-selective cyclo-oxygenase COX-1/COX-2 inhibitors whether applied topically or systemically (such as piroxicam, diclofenac, propionic acids such as naproxen, flubiprofen, fenoprofen, ketoprofen and ibuprofen, fenamates such as mefenamic acid, indomethacin, sulindac, azapropazone, pyrazolones such as phenylbutazone, salicylates such as aspirin), COX-2 inhibitors (such as meloxicam, celecoxib, rofecoxib, valdecoxib, lumarocoxib, parecoxib and etoricoxib); glucocorticosteroids (whether administered by topical, oral, intramuscular, intravenous, or intra-articular routes); methotrexate, lefunomide; hydroxychloroquine, d-penicillamine, auranofin or other parenteral or oral gold preparations.

The present invention still further relates to the combination of a compound of the invention and a leukotriene biosynthesis inhibitor, 5-lipoxygenase (5-LO) inhibitor or 5-lipoxygenase activating protein (FLAP) antagonist such as; zileuton; ABT-761; fenleuton; tepoxalin; Abbott®-79175; Abbott®-85761; a N-(5-substituted)-thiophene-2-alkylsulfonamide; 2,6-di-tert-butylphenolhydrazones; a methoxytetrahydropyrans such as Zeneca® ZD-2138; the compound SB-210661; a pyridinyl-substituted 2-cyanonaphthalene compound such as L-739,010; a 2-cyanoquinoline compound such as L-746,530; or an indole or quinoline compound such as MK-591, MK-886, and BAY×1005.

The present invention further relates to the combination of a compound of the invention and a receptor antagonist for leukotrienes (LTB4, LTC4, LTD4, and LTE4) selected from the group consisting of the phenothiazin-3-1s such as L-651,392; amidino compounds such as CGS-25019c; benzoxalamines such as ontazolast; benzenecarboximidamides such as BIIL 284/260; and compounds such as zafirlukast, ablukast, montelukast, pranlukast, verlukast (MK-679), RG-12525, Ro-245913, iralukast (CGP 45715A), and BAY×7195.

The present invention still further relates to the combination of a compound of the invention and a phosphodiesterase (PDE) inhibitor such as a methylxanthanine including theophylline and aminophylline; a selective PDE isoenzyme inhibitor including a PDE4 inhibitor an inhibitor of the isoform PDE4D, or an inhibitor of PDE5.

The present invention further relates to the combination of a compound of the invention and a histamine type 1 receptor antagonist such as cetirizine, loratadine, desloratadine, fexofenadine, acrivastine, terfenadine, astemizole, azelastine, levocabastine, chlorpheniramine, promethazine, cyclizine, or mizolastine; applied orally, topically or parenterally.

The present invention still further relates to the combination of a compound of the invention and a gastroprotective histamine type 2 receptor antagonist.

The present invention further relates to the combination of a compound of the invention and an antagonist of the histamine type 4 receptor.

The present invention still further relates to the combination of a compound of the invention and an alpha-1/alpha-2 adrenoceptor agonist vasoconstrictor sympathomimetic agent, such as propylhexedrine, phenylephrine, phenylpropanolamine, ephedrine, pseudoephedrine, naphazoline hydrochloride, oxymetazoline hydrochloride, tetrahydrozoline hydrochloride, xylometazoline hydrochloride, tramazoline hydrochloride or ethylnorepinephrine hydrochloride.

The present invention further relates to the combination of a compound of the invention and an anticholinergic agent including muscarinic receptor (M1, M2, and M3) antagonists such as atropine, hyoscine, glycopyrrrolate, ipratropium bromide, tiotropium bromide, oxitropium bromide, pirenzepine or telenzepine.

The present invention still further relates to the combination of a compound of the invention together with a beta-adrenoceptor agonist (including beta receptor subtypes 1-4) such as isoprenaline, salbutamol, formoterol, salmeterol, terbutaline, orciprenaline, bitolterol mesylate, and pirbuterol.

The present invention further relates to the combination of a compound of the invention and a chromone, such as sodium cromoglycate or nedocromil sodium.

The present invention still further relates to the combination of a compound of the invention together with an insulin-like growth factor type I (IGF-1) mimetic.

The present invention still further relates to the combination of a compound of the invention and a glucocorticoid, such as flunisolide, triamcinolone acetonide, beclomethasone dipropionate, budesonide, fluticasone propionate, ciclesonide or mometasone furoate.

The present invention still further relates to the combination of a compound of the invention together with an inhibitor of matrix metalloproteases (MMPs), i.e., the stromelysins, the collagenases, and the gelatinases, as well as aggrecanase; especially collagenase-1 (MMP-1), collagenase-2 (MMP-8), collagenase-3 (MMP-13), stromelysin-1 (MMP-3), stromelysin-2 (MMP-10), and stromelysin-3 (MMP-11) and MMP-9 and MMP-12.

The present invention still further relates to the combination of a compound of the invention together with modulators of chemokine receptor function such as antagonists of CCR1, CCR2, CCR2A, CCR2B, CCR3, CCR4, CCR5, CCR6, CCR7, CCR8, CCR9, CCR10 and CCR11 (for the C—C family); CXCR1, CXCR2, CXCR3, CXCR4 and CXCR5 (for the C—X—C family) and CX3CR1 for the C—X3-C family.

The present invention still further relates to the combination of a compound of the invention together with a cytokine or modulator of cytokine function, including alpha-, beta-, and gamma-interferon; interleukins (IL) including IL1 to 15, and interleukin antagonists or inhibitors, including agents which act on cytokine signalling pathways.

The present invention still further relates to the combination of a compound of the invention together with an immunoglobulin (Ig) or Ig preparation or an antagonist or antibody modulating Ig function such as anti-IgE (omalizumab).

The present invention further relates to the combination of a compound of the invention and another systemic or topically-applied anti-inflammatory agent, such as thalidomide or a derivative thereof, a retinoid, dithranol or calcipotriol.

The present invention further relates to the combination of a compound of the invention together with an antibacterial agent such as a penicillin derivative, a tetracycline, a macrolide, a beta-lactam, a fluoroquinolone, metronidazole, an inhaled aminoglycoside; an antiviral agent including acyclovir, famciclovir, valaciclovir, ganciclovir, cidofovir, amantadine, rimantadine, ribavirin, zanamavir and oseltamavir; a protease inhibitor such as indinavir, nelfinavir, ritonavir, and saquinavir; a nucleoside reverse transcriptase inhibitor such as didanosine, lamivudine, stavudine, zalcitabine or zidovudine; or a non-nucleoside reverse transcriptase inhibitor such as nevirapine or efavirenz.

The present invention will now be further explained by reference to the following illustrative examples in which the following abbreviations are used:

-   -   EtOAc ethyl acetate     -   DCM dichloromethane     -   NMP N-methylpyrrolidine     -   NBS N-bromosuccinimide     -   DMF N,N-dimethylformamide     -   DMSO dimethylsulfoxide     -   THF tetrahydrofuran     -   MeOH methanol     -   TFA trifluoroacetic acid     -   HCl hydrogen chloride     -   K₂CO₃ potassium carbonate     -   NaHCO₃ sodium hydrogen carbonate     -   Et₃N triethylamine     -   MeCN acetonitrile     -   rt room temperature     -   h hours     -   min minutes     -   M molar     -   MS mass spectrometry     -   PyBop Benzotriazol-1-yloxytripyrrolidinophosphonium         hexafluorophosphate     -   APCI atmospheric chemical ionisation method     -   ESI electron spray ionisation method     -   NMR nuclear magnetic resonance     -   HCl hydrochloric acid

Unless otherwise stated organic solutions were dried over magnesium sulphate. RPHPLC denotes Reversed Phase Preparative High Performance Liquid Chromatography using Waters® Symmetry® C8, XTerra® or Phenomenex® Gemini™ columns using acetonitrile and either aqueous ammonium acetate, ammonia, formic acid or trifluoroacetic acid as buffer where appropriate. Column chromatography was carried out on silica gel.

EXAMPLE 1 N-[3-(6-Amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl]-N-benzylacetamide

(i) 2-Chloro-9-(tetrahydro-2H-pyran-2-yl)-9H-purin-6-amine

2,6-Dichloro-9-(tetrahydro-2H-pyran-2-yl)-9H-purine (55 g) was dissolved in 7N-aqueous ammonia in methanol (500 ml) and heated at 100° C. in a sealed flask for 6 h. The reaction mixture was cooled to rt and left overnight. Filtration afforded the subtitle compound. Yield 40 g.

¹H NMR δ (CDCl₃) 8.02 (1H, s), 5.94 (2H, brs), 5.71 (1H, dd), 4.15-4.22 (1H, m), 3.75-3.82 (1H, m), 1.27-2.12 (6H, m).

(ii) 2-Butoxy-9-(tetrahydro-2H-pyran-2-yl)-9H-purin-6-amine

The product from step (i) (40 g) was dissolved in 19% (w/w)-sodium butoxide in butanol (250 ml). The reaction mixture was stirred under reflux for 6 h. The resultant suspension was cooled to rt, diluted with water and extracted with diethyl ether. The combined organic phase was washed with water, dried and concentrated in vacuo. The subtitle compound was crystallized from diethyl ether/isohexane (1/1, 300 ml) and obtained by filtration. Yield 19 g.

¹H NMR δ (CDCl₃) 7.87 (1H, s), 5.56-5.68 (3H, m), 4.31-4.35 (2H, t), 4.14-4.17 (1H, m), 3.76-3.80 (1H, m), 1.49-2.08 (10H, m), 0.98 (3H, t).

(iii) 8-Bromo-2-butoxy-9-(tetrahydro-2H-pyran-2-yl)9H-purin-6-amine

The product from step (ii) (30 g) was dissolved in dry DCM (200 ml). The solution was stirred at rt whilst N-bromosuccinimide (27 g) was added portion wise. The mixture was stirred at rt overnight. 20% (w/v)-Sodium sulfate (200 ml) was added and the separated aqueous phase extracted with DCM. The combined organic phase was washed with saturated NaHCO₃ solution and brine. After concentration in vacuo, the residue was dissolved in EtOAc, washed with water, brine and dried. The solution was filtered through silica gel. The filtrate was concentrated in vacuo and dissolved in a mixture of diethyl ether and isohexane (1/1, 200 ml) to give the subtitle compound (26 g). The solvent was removed to give a residue, which was purified by column chromatography (EtOAc/isohexane), which afforded 2.5 g. The solids were combined to give the subtitle compound as a yellow solid. Yield 28.5 g. Melting point: 148-150° C.

¹H NMR δ (CDCl₃) 5.59-5.64 (3H, m), 4.32 (2H, m), 4.17 (1H, m), 3.74 (1H, m), 3.08 (1H, m), 2.13 (1H, d), 1.48-1.83 (8H, m), 0.98 (3H, t).

(iv) 2-Butoxy-8-methoxy-9-(tetrahydro-2H-pyran-2-yl)9H-purin-6-amine

Sodium (3.7 g) was added to absolute methanol (400 ml) under a nitrogen atmosphere. To this solution was added the product (28.5 g) from step (iii) and the mixture was stirred at 65° C. for 9 h. The mixture was concentrated in vacuo and 500 ml of water added. The aqueous phase was extracted with EtOAc and washed with brine and dried. The subtitle compound was obtained after crystallisation from diethyl ether. Yield 14.2 g.

¹H NMR δ (CDCl₃) 5.51 (1H, dd), 5.28 (2H, brs), 4.29 (2H, t), 4.11-4.14 (4H, m), 3.70 (1H, m), 2.76-2.80 (1H, m), 2.05 (1H, d), 1.47-1.81 (8H, m), 0.97 (3H, t).

(v) 2-Butoxy-8-methoxy-9H-purin-6-amine, TFA salt

The product from step (iv) (24 g) was dissolved in absolute methanol (300 ml) and 30 ml of TFA was added. The reaction mixture was stirred at rt for 3 days and concentrated in vacuo. The subtitle compound was obtained as a white crystalline solid after trituration with methanol/EtOAc. Yield 21 g.

¹H NMR δ (CD₃OD), 4.48 (2H, t), 4.15 (3H, s), 1.80 (2H, quintet), 1.50 (2H, sextet), 0.99 (3H, t).

(vi) 2-[3-(6-Amino-2-butoxy-8-methoxy-9H-purin-9-yl)propyl]-1H-isoindole-1,3(2H)-dione

The product from step (v) (15 g) was dissolved in dry DMF (200 ml) and 18 g of K₂CO₃ added. After the suspension was stirred at rt for 15 min, 2-(3-bromopropyl)-1H-isoindole-1,3(2H)-dione (14 g) was added the suspension vigorously stirred at rt for 10 h. The reaction mixture was extracted with EtOAc, washed with water and brine and dried. The subtitle compound was obtained after crystallisation from EtOAc/diethyl ether. Yield 16 g.

¹H NMR δ (DMSO-d₆) 7.83 (4H, m), 6.73 (2H, brs), 4.06 (2H, t), 4.01 (3H, s), 3.89 (2H, t), 3.58 (21-1, t), 2.07-2.14 (2H, m), 1.55-1.62 (2H, m), 1.31-1.40 (2H, m), 0.90 (3H, t).

(vii) 9-(3-Aminopropyl)-2-butoxy-8-methoxy-9H-purin-6-amine

The product from step (vi) (1 g) was dissolved in ethanol (10 ml) and hydrazine monohydrate (1 ml) was added and stirred at ambient temperature for 10 h. The resultant was concentrated under reduced pressure and the residue suspended in DCM (10 ml) and stirred for 1 h. The suspension was filtered, washed with DCM. The solution was washed with water and dried. The solution was concentrated under reduced pressure to give the subtitled compound. Yield 700 mg.

¹H NMR δ (DMSO-d₆) 6.77 (21-1, brs), 4.16 (2H, t), 4.05 (3H, s), 3.89 (2H, t), 2.46-2.52 (2H, m), 1.61-1.76 (4H, m), 1.35-1.45 (2H, m), 0.92 (31-1, t).

(viii) 6-Amino-9-[3-(benzylamino)propyl]-2-butoxy-7,9-dihydro-8H-purin-8-one, dihydrochloride

The product from step (vii) (4 g) and benzaldehyde (1.6 g) were dissolved in THF (40 ml) and stirred at rt for 24 h. Sodium borohydride (0.8 g) and 5 drops of methanol was added and stirred at a rt overnight. The solvent was evaporated under reduced pressure and the residue partitioned between EtOAc and brine. The organic layer was separated, washed with water, dried and evaporated under reduced pressure. The residue was dissolved in MeOH (100 ml), conc. HCl (10 ml) added and stirred at rt for 72 h. The solvent was evaporated under reduced pressure and the residue triturated with MeOH/EtOAc. Yield 3.64 g.

¹H NMR δ (DMSO-d₆) 10.96 (1H, s); 9.23 (2H, brs); 7.53-7.38 (5H, m); 4.26 (2H, t); 4.11 (2H, t); 3.78 (2H, t); 2.93-2.91 (2H, m); 2.10-2.03 (2H, m); 1.71-1.64 (2H, m); 1.46-1.36 (2H, m); 0.93 (3H, t).

MS: APCI (+ve): 371.

(ix) N-[3-(6-Amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl]-N-benzylacetamide

Acetylchloride (0.08 ml) was added to a mixture of the product from step (viii) (250 mg) and triethylamine (0.6 ml) in NMP (5 ml) and stirred for 2 h. The mixture was purified by to RPHPLC, yield 85 mg.

¹H NMR δ (DMSO-d₆) rotomers present 9.86 and 9.82 (1H, 2×s); 7.35-7.10 (5H, m); 6.41 and 6.39 (2H, 2×s); 4.56 and 4.46 (2H, 2×s); 4.14-4.10 (2H, m); 3.68-3.60 (2H, m); 3.25-3.18 (2H, m); 2.01 and 1.99 (3H, 2×s); 1.95-1.80 (2H, m); 1.65-1.60 (2H, m); 1.41-1.35 (2H, m); 0.91 (3H, t).

MS: APCI (+ve): 413.

EXAMPLE 2 N-[3-(6-Amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl]-N-benzyl-2-methoxyacetamide

The title compound was prepared by the method of example 1 using methoxyacetyl chloride.

¹H NMR δ (DMSO-d₆) rotomers present 9.87 (1H, s); 7.34-7.11 (5H, m); 6.42 and 6.40 (2H, 2×s); 4.51 and 4.48 (2H, 2×s); 4.14 and 4.11 (2H, m); 4.07 and 4.05 (2H, 2×s); 3.67-3.60 (2H, m); 3.26-3.13 (5H, m); 1.96-1.81 (2H, m); 1.66-1.59 (2H, m); 1.42-1.33 (2H, m); 0.91 (3H, t).

MS: APCI (+ve): 443.

EXAMPLE 3 Methyl 4-[[3-(6-amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl](benzyl)amino]-4-oxobutanoate

PyBop (0.47 g) was added to a mixture of the product from example 1 step (viii) (0.25 g), Et₃N (0.7 ml) and succinic acid monomethyl ester (0.16 g) in DMF (8 ml) and stirred at rt for 4 days. MeOH (10 ml) was added, the solvent evaporated under reduced pressure and the residue purified by RPHPLC, yield 46 mg.

¹H NMR δ (DMSO-d₆) rotomers present 9.86 and 9.82 (1H, 2×s); 7.34-7.09 (5H, m); 6.41 and 6.39 (2H, 2×s); 4.60 and 4.47 (2H, 2×s); 4.14-4.10 (2H, m); 3.70-3.58 (2H, m); 3.57 to and 3.56 (3H, 2×s); 3.26-3.21 (2H, m); 2.60-2.57 (2H, m); 1.98-1.78 (2H, m); 1.65-1.60 (2H, m); 1.40-1.34 (2H, m); 0.91 (3H, t).

MS: APCI (+ve): 485.

Examples 4-10 were prepared by the same method as Example 3.

EXAMPLE 4 N-[3-(6-Amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl]-N-benzyl-3-methoxypropanamide

¹H NMR δ (DMSO-d₆) rotomers present 9.86 and 9.82 (1H, 2×s); 7.33-7.10 (5H, m); 6.41 and 6.39 (2H, 2×s); 4.58 and 4.48 (2H, 2×s); 4.12 (2H, t); 3.68-3.50 (4H, m); 3.25-3.23 (2H, m); 3.20 and 3.17 (3H, 2×s); 1.96-1.78 (2H, m); 1.67-1.58 (2H, m); 1.40-1.35 (2H, m); 0.91 (3H, t).

MS: APCI (+ve): 457.

EXAMPLE 5 N-[3-(6-Amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl]-N-benzyl-N′,N′-dimethylsuccinamide

¹H NMR δ (DMSO-d₆) rotomers present 9.85 (1H, s); 7.35-7.10 (5H, m); 6.41 and 6.39 (2H, 2×s); 4.60 and 4.47 (2H, 2×s); 4.13-4.10 (2H, m); 3.69-3.60 (2H, m); 3.27-3.20 (2H, m); 2.97 and 2.95 (3H, 2×s); 2.80 and 2.79 (3H, 2×s); 2.54 (2H, s); 1.98-1.79 (2H, m); 1.64-1.59 (2H, m); 1.40-1.35 (2H, m); 0.91 (3H, t).

MS: APCI (+ve): 498.

EXAMPLE 6 N-[3-(6-Amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl]-N-benzyl-2-[4-(methylsulfonyl)phenyl]acetamide

¹H NMR δ (DMSO-d₆) rotomers present 9.89 and 9.82 (1H, 2×s); 7.84-7.81 (2H, m); 7.44-7.11 (7H, m); 6.44-6.39 (2H, 2×s); 4.66 and 4.50 (2H, 2×s); 4.13-4.08 (2H, m); 3.84 (2H, s); 3.70-3.60 (2H, m); 3.29-3.26 (2H, m); 3.20 and 3.18 (3H, 2×s); 2.01-1.80 (2H, m); 1.66-1.56 (2H, m); 1.41-1.29 (2H, m); 0.92-0.86 (3H, m).

MS: APCI (+ve): 567.

EXAMPLE 7 N-[3-(6-Amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl]-N-benzyl-2-(4-benzylpiperazin-1-yl)acetamide

¹H NMR δ (DMSO-d₆) rotomers present 9.86 and 9.81 (1H, 2×s); 7.33-7.12 (10H, m); 6.41 and 6.39 (2H, 2×s); 4.66 and 4.48 (2H, 2×s); 4.15-4.09 (2H, m); 3.69-3.56 (2H, m); 3.41 and 3.35 (2H, 2×s); 3.32-3.14 (2H, m); 3.11 and 3.01 (2H, 2×s); 2.43-2.18 (8H, m); 2.02-1.75 (2H, m); 1.66-1.58 (2H, m); 1.41-1.31 (2H, m); 0.93-0.87 (3H, m).

MS: APCI (+ve): 587.

EXAMPLE 8 N-[3-(6-Amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl]-N-benzyl-2-(3,5-dimethyl-1H-1,2,4-triazol-1-yl)acetamide

¹H NMR δ (DMSO-d₆) rotomers present 9.86 (1H, brs); 7.39-7.12 (5H, m); 6.42 and 6.39 (2H, 2×s); 5.12 and 5.03 (2H, 2×s); 4.66 and 4.49 (2H, 2×s); 4.11 (2H, t); 3.73-3.61 (2H, m); 3.28-3.24 (2H, m); 2.24 and 2.20 (3H, 2×s); 2.15 and 2.12 (3H, 2×s); 2.06-1.80 (2H, m); 1.64-1.57 (2H, m); 1.40-1.33 (2H, m); 0.93-0.88 (3H, m).

MS: APCI (+ve): 508.

EXAMPLE 9 N-[3-(6-Amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl]-N-benzyl-3-pyrazin-2-ylpropanamide

¹H NMR δ (DMSO-d₆) rotomers present 9.84 and 9.82 (1H, 2×s); 8.55 (1H, d); 8.50 (1H, d); 8.43 (1H, dd); 7.32-7.04 (5H, m); 6.40 (2H, s); 4.61 and 4.46 (2H, 2×s); 4.13-4.08 (2H, m); 3.70-3.57 (2H, m); 3.29-3.21 (2H, m); 3.04-3.00 (2H, m); 2.83-2.79 (2H, m); 1.97-1.78 (2H, m); 1.64-1.58 (2H, m); 1.38-1.34 (2H, m); 0.92-0.87 (3H, m).

MS: APCI (+ve): 505.

EXAMPLE 10 N-[3-(6-Amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl]-N-benzyl-N³,N³-dimethyl-β-alaninamide

¹H NMR δ (DMSO-d₆) rotomers present 9.87 and 9.82 (1H, 2×s); 7.36-7.10 (5H, m); 6.41 and 6.39 (2H, 2×s); 4.59 and 4.47 (2H, 2×s); 4.12 (2H, t); 3.69-3.60 (2H, m); 3.28-3.18 (2H, m); 2.46-2.32 (4H, m); 2.06-2.04 (6H, 2×s); 1.96-1.80 (2H, m); 1.65-1.59 (2H, m); 1.41-1.34 (2H, m); 0.93-0.88 (3H, m).

MS: APCI (+ve): 470.

Biological Assay

Human TLR7 Assay

Recombinant human TLR7 was stably expressed in a HEK293 cell line already stably expressing the pNiFty2-SEAP reporter plasmid; integration of the reporter gene was maintained by selection with the antibiotic zeocin. The most common variant sequence of human TLR7 (represented by the EMBL sequence AF240467) was cloned into the mammalian cell expression vector pUNO and transfected into this reporter cell-line. Transfectants with stable expression were selected using the antibiotic blasticidin. In this reporter cell-line, expression of secreted alkaline phosphatase (SEAP) is controlled by an NFkB/ELAM-1 composite promoter comprising five NFkB sites combined with the proximal ELAM-1 promoter. TLR signaling leads to the translocation of NFkB and activation of the promoter results in expression of the SEAP gene. TLR7-specific activation was assessed by determining the level of SEAP produced following overnight incubation of the cells at 37° C. with the standard compound in the presence of 0.1% (v/v) dimethylsulfoxide (DMSO). Concentration dependent induction of SEAP production by compounds was expressed as the concentration of compound which produced half of the maximal level of SEAP induction for that compound (pEC50). The results obtained are shown in Table 1 following.

TABLE 1 Compound of Example No. pEC50 1 7.2 2 7.3 3 7.4 4 7.1 5 7.1 6 7.1 7 8.1 8 6.8 9 7.3 10 7.5 

1. A compound of formula

wherein R¹ represents hydrogen, hydroxyl, or a C₁-C₆ alkoxy, C₂-C₅ alkoxycarbonyl, C₁-C₆ haloalkyl, C₁-C₆ haloalkoxy, C₆-C₁₀ aryl, C₅-C₁₀ heteroaryl or C₃-C₈ cycloalkyl group, each group being optionally substituted by one or more substituents independently selected from halogen, hydroxyl, C₁-C₆ alkyl, C₁-C₆ haloalkyl, C₁-C₆ alkoxy, C₁-C₆ haloalkoxy, C₂-C₅ alkoxycarbonyl, amino, mono-C₁-C₆ alkylamino and di-C₁-C₆ alkylamino; Y¹ represents a single bond or C₁-C₆ alkylene; X¹ represents a single bond, an oxygen or sulphur atom, sulphonyl or NR³; Z¹ represents a C₂-C₆ alkylene or C₃-C₈ cycloalkylene group, each group being optionally substituted by at least one hydroxyl; X² represents NR⁴; Y² represents a single bond or C₁-C₆ alkylene; n is an integer 0, 1 or 2; each R² group independently represents halogen, cyano, S(O)_(m)R⁹, OR¹⁰, SO₂NR¹⁰R¹¹, CONR¹⁰R¹¹, NR¹⁰R¹¹, NR¹⁰SO₂R⁹, NR¹⁰CO₂R⁹, NR¹⁰COR⁹, C₆-C₁₀ aryl, C₅-C₁₀ heteroaryl, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl or C₃-C₈ cycloalkyl, the latter six groups being optionally substituted by one or more substituents independently selected from halogen, cyano, S(O)_(p)R¹², OR¹³, SO₂NR¹³R¹⁴, CONR¹³R¹⁴, NR¹³R¹⁴, NR¹³SO₂R¹², NR¹³CO₂R¹², NR¹³COR¹², C₁-C₆ alkyl, C₁-C₃ haloalkyl and C₃-C₈ cycloalkyl; R³ represents hydrogen or C₁-C₆ alkyl; R⁴ represents CO₂R⁵, SO₂R⁵, COR⁵, SO₂NR⁶R⁷ or CONR⁶R⁷; R⁵ represents (i) a 3- to 8-membered saturated heterocyclic ring containing 1 or 2 ring heterogroups independently selected from NR⁸, S(O)_(q) or oxygen, the ring being optionally substituted by one or more substituents independently selected from halogen, hydroxyl, C₁-C₆ alkyl and C₁-C₆ alkoxy, or (ii) a C₆-C₁₀ aryl or C₅-C₁₀ heteroaryl group, each of which may be optionally substituted by one or more substituents independently selected from halogen, cyano, C₁-C₆ alkyl, C₁-C₃ haloalkyl, S(O)_(r)R⁹, OR¹⁰, CO₂R¹⁰, SO₂NR¹⁰R¹¹, CONR¹⁰R¹¹, NR¹⁰R¹¹, NR¹⁰SO₂R⁹, NR¹⁰CO₂R⁹ and NR¹⁰COR⁹, or (iii) a C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl or C₃-C₈ cycloalkyl group, each of which may be optionally substituted by one or more substituents independently selected from halogen, cyano, C₃-C₈ cycloalkyl, S(O)_(t)R¹², OR¹³, COR¹³, CO₂R¹³, SO₂NR¹³R¹⁴, CONR¹³R¹⁴, NR⁶R⁷, NR¹³SO₂R¹², NR¹³CO₂R¹², NR¹³COR¹², C₆-C₁₀ aryl and C₅-C₁₀ heteroaryl, the latter two substituents themselves being optionally substituted by one or more substituents independently selected from C₁-C₆ alkyl, halogen, hydroxy, methylsulphonyl and cyano; R⁶ represents a hydrogen atom or a group selected from C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₈ cycloalkyl group and a heterocyclic moiety, which group may be optionally substituted by one or more substituents independently selected from halogen, hydroxyl, oxo, cyano, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₈ cycloalkyl, OR¹⁵, S(O)_(v)R¹⁵, CO₂R¹⁶, COR¹⁶, NR¹⁶R¹⁷, CONR¹⁶R¹⁷, NR¹⁶COR¹⁷, NR¹⁶CO₂R¹⁵, SO₂NR¹⁶R¹⁷, NR¹⁶SO₂R¹⁵, C₆-C₁₀ aryl, C₅-C₁₀ heteroaryl and a heterocyclic moiety, the latter three substituents themselves being optionally substituted by one or more substituents independently selected from C₁-C₆ alkyl, C₃-C₈ cycloalkyl, halogen, S(O)_(w)R¹⁵, CO₂R¹⁶, COR¹⁶, hydroxy and cyano, and R⁷ represents a hydrogen atom or a C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl or C₃-C₈ cycloalkyl group, each group being optionally substituted by one or more substituents independently selected from halogen, C₃-C₈ cycloalkyl, C₆-C₁₀ aryl, C₅-C₁₀ heteroaryl, carboxy, cyano, OR¹⁵, hydroxy and NR¹⁸R¹⁹, or R⁶ and R⁷ together with the nitrogen atom to which they are attached form a 3- to 8-membered saturated or partially saturated heterocyclic ring optionally containing a further ring heterogroup selected from nitrogen, S(O)_(x) and oxygen, the heterocyclic ring being optionally substituted by one or more substituents independently selected from halogen, hydroxyl, carboxyl, cyano, OR²⁰, NR²¹R²², S(O)_(y)R²³, COR²⁴, CO₂R²⁴, NR²⁴R²⁵, CONR²⁴R²⁵, NR²⁴COR²⁵, NR²⁴CO₂R²³, SO₂NR²⁴R²⁵, NR²⁴SO₂R²³, C₆-C₁₀ aryl, benzyl, C₅-C₁₀ heteroaryl, a heterocyclic moiety, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₈ cycloalkyl, the latter eight substituents themselves being optionally substituted by one or more substituents independently selected from halogen, oxo, cyano, OR²¹, S(O)_(z)R²³, COR²⁴, CO₂R²⁴ and NR²⁴R²⁵; each R⁸, R¹⁰, R¹¹, R¹³, R¹⁴, R¹⁶, R¹⁷, R¹⁸, R¹⁹, R²¹, R²², R²⁴ and R²⁵ independently represents a hydrogen atom or a C₁-C₆ alkyl or C₃-C₆ cycloalkyl group; each R⁹, R¹², R¹⁵ and R²³ independently represents C₁-C₆ alkyl or C₃-C₆ cycloalkyl; R²⁰ represents a C₁-C₆ alkyl group optionally substituted by one or more substituents independently selected from halogen, hydroxyl and OR²³; m, p, q, r, t, v, w, x, y and z each independently represent an integer 0, 1 or 2; and A represents a C₆-C₁₀ aryl or C₅-C₁₂ heteroaryl group; or a pharmaceutically acceptable salt thereof.
 2. The compound according to claim 1, wherein R¹ represents hydrogen, or a pharmaceutically acceptable salt thereof.
 3. The compound according to claim 1, wherein Y¹ represents C₁-C₆ alkylene, or a pharmaceutically acceptable salt thereof.
 4. The compound according to claim 1, wherein X¹ represents an oxygen atom, or a pharmaceutically acceptable salt thereof.
 5. The compound according to claim 1, wherein Z¹ represents C₂-C₆ alkylene, or a pharmaceutically acceptable salt thereof.
 6. The compound according to claim 1, wherein X² represents NR⁴ and R⁴ represents COR⁵, or a pharmaceutically acceptable salt thereof.
 7. The compound according to claim 1, wherein R⁵ represents C₁-C₄ alkyl optionally substituted by one or two substituents independently selected from fluorine, chlorine, cyano, C₃-C₆ cycloalkyl, S(O)_(t)R¹², OR¹³, COR¹³, CO₂R¹³, SO₂NR¹³R¹⁴, CONR¹³R¹⁴, NR⁶R⁷, NR¹³SO₂R¹², NR¹³CO₂R¹², NR¹³COR¹², phenyl and C₅-C₆ heteroaryl, the latter two substituents themselves being optionally substituted by one, two, three or four substituents independently selected from C₁-C₄ alkyl, fluorine, chlorine, hydroxy, methylsulphonyl and cyano, or a pharmaceutically acceptable salt thereof.
 8. The compound according to claim 1, wherein Y² represents C₁-C₆ alkylene, or a pharmaceutically acceptable salt thereof.
 9. The compound according to claim 1, wherein A represents C₆-C₁₀ aryl, or a pharmaceutically acceptable salt thereof.
 10. The compound according to claim 1 selected from: N-[3-(6-Amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl]-N-benzylacetamide, N-[3-(6-Amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl]-N-benzyl-2-methoxyacetamide, Methyl 4-[[3-(6-amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl](benzyl)amino]-4-oxobutanoate, N-[3-(6-Amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl]-N-benzyl-3-methoxypropanamide, N-[3-(6-Amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl]-N-benzyl-N′,N′-dimethylsuccinamide, N-[3-(6-Amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl]-N-benzyl-2-[4-(methylsulfonyl)phenyl]acetamide, N-[3-(6-Amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl]-N-benzyl-2-(4-benzylpiperazin-1-yl)acetamide, N-[3-(6-Amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl]-N-benzyl-2-(3,5-dimethyl-1H-1,2,4-triazol-1-yl)acetamide, N-[3-(6-Amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl]-N-benzyl-3-pyrazin-2-ylpropanamide, and N-[3-(6-Amino-2-butoxy-8-oxo-7,8-dihydro-9H-purin-9-yl)propyl]-N-benzyl-N³,N³-dimethyl-β-alaninamide, and pharmaceutically acceptable salts thereof.
 11. A process for the preparation of a compound of formula (I) or a pharmaceutically acceptable salt thereof as claimed in claim 1 which comprises, (a) when R⁴ represents a group COR⁵, reacting a compound of formula

wherein n, R¹, R², A, X¹, Y¹, Z¹ and Y² are as defined in claim 1, with a compound of formula (III), R⁵—C(O)-L¹, wherein L¹ represents halogen or hydroxy and R⁵ is as defined in claim 1, in the presence of a base or a coupling reagent as required; (b) when R⁴ represents a group COR⁵ and R⁵ represents a group C₁-C₆ alkyl-NR⁶R⁷, reacting a compound of formula

wherein R³⁰ represents a C₁-C₆ alkyl group, L² represents a leaving group and n, R¹, R², A, X¹, Y¹, Z¹ and Y² are as defined in claim 1, with a compound of formula (V), NHR⁶R⁷, wherein R⁶ and R⁷ are as defined in claim 1, in the presence of a base; (c) when R⁴ represents a group SO₂R⁵, reacting a compound of formula (II) as defined in (a) above with a compound of formula (VI), L³-S(O)₂—R⁵, wherein L³ represents a leaving group and R⁵ is as defined in claim 1, in the presence of a base; (d) when R⁴ represents a group CO₂R⁵, reacting a compound of formula (II) as defined in (a) above with a compound of formula (VII), L⁴-C(O)—OR⁵, wherein L⁴ represents a leaving group and R⁵ is as defined in claim 1, in the presence of a base; (e) when R⁴ represents a group SO₂NR⁶R⁷, reacting a compound of formula (II) as defined in (a) above with a compound of formula (VIII), L⁵-S(O)₂—NR⁶R⁷, wherein L⁵ represents a leaving group and R⁶ and R⁷ are as defined in claim 1, in the presence of a base; or (f) when R⁴ represents a group CONR⁶R⁷, reacting a compound of formula (II) as defined in (a) above with a compound of formula (IX), L⁶-C(O)—NR⁶R⁷, wherein L⁶ represents a leaving group and R⁶ and R⁷ are as defined in claim 1, in the presence of a base; and optionally thereafter carrying out one or more of the following procedures: removing any protecting groups, forming a pharmaceutically acceptable salt.
 12. A pharmaceutical composition comprising a compound of formula (I) or a pharmaceutically acceptable salt thereof as claimed in claim 1 or claim 10 in association with a pharmaceutically acceptable adjuvant, diluent or carrier. 